We investigated the role of nuclear factor erythroid 2-related factor 2 (Nrf2) in renin-angiotensin system (RAS) gene expression in renal proximal tubule cells (RPTCs) and in the development of systemic hypertension and kidney injury in diabetic Akita mice. We used adult male Akita Nrf2 knockout mice and Akita mice treated with trigonelline (an Nrf2 inhibitor) or oltipraz (an Nrf2 activator). We also examined rat immortalized RPTCs (IRPTCs) stably transfected with control plasmids or plasmids containing rat angiotensinogen (Agt), angiotensin-converting enzyme (ACE), angiotensin-converting enzyme-2 (Ace2), or angiotensin 1-7 (Ang 1-7) receptor (MasR) gene promoters. Genetic deletion of Nrf2 or pharmacological inhibition of Nrf2 in Akita mice attenuated hypertension, renal injury, tubulointerstitial fibrosis, and the urinary albumin/creatinine ratio. Furthermore, loss of Nrf2 upregulated RPTC Ace2 and MasR expression, increased urinary Ang 1-7 levels, and downregulated expression of Agt, ACE, and profibrotic genes in Akita mice. In cultured IRPTCs, Nrf2 small interfering RNA transfection or trigonelline treatment prevented high glucose stimulation of Nrf2 nuclear translocation, Agt, and ACE transcription with augmentation of Ace2 and MasR transcription, which was reversed by oltipraz. These data identify a mechanism, Nrf2-mediated stimulation of intrarenal RAS gene expression, by which chronic hyperglycemia induces hypertension and renal injury in diabetes.

. Dual RAS blockade normalizes angiotensin-converting enzyme-2 expression and prevents hypertension and tubular apoptosis in Akita angiotensinogen-transgenic mice. Am J Physiol Renal Physiol 302: F840 -F852, 2012. First published December 28, 2011 doi:10.1152/ajprenal.00340.2011.-We investigated the effects of dual renin-angiotensin system (RAS) blockade on angiotensin-converting enzyme-2 (Ace2) expression, hypertension, and renal proximal tubular cell (RPTC) apoptosis in type 1 diabetic Akita angiotensinogen (Agt)-transgenic (Tg) mice that specifically overexpress Agt in their RPTCs. Adult (11 wk old) male Akita and Akita Agt-Tg mice were treated with two RAS blockers (ANG II receptor type 1 blocker losartan, 30 mg·kg Ϫ1 ·day Ϫ1 ) and angiotensinconverting enzyme (ACE) inhibitor perindopril (4 mg·kg Ϫ1 ·day Ϫ1 ) in drinking water. Same-age non-Akita littermates and Agt-Tg mice served as controls. Blood pressure, blood glucose, and albuminuria were monitored weekly. The animals were euthanized at age 16 wk. The left kidneys were processed for immunohistochemistry and apoptosis studies. Renal proximal tubules were isolated from the right kidneys to assess gene and protein expression. Urinary ANG II and ANG 1-7 were quantified by ELISA. RAS blockade normalized renal Ace2 expression and urinary ANG 1-7 levels (both of which were low in untreated Akita and Akita Agt-Tg), prevented hypertension, albuminuria, tubulointerstitial fibrosis and tubular apoptosis, and inhibited profibrotic and proapoptotic gene expression in RPTCs of Akita and Akita Agt-Tg mice compared with non-Akita controls. Our results demonstrate the effectiveness of RAS blockade in preventing intrarenal RAS activation, hypertension, and nephropathy progression in diabetes and support the important role of intrarenal Ace2 expression in modulating hypertension and renal injury in diabetes.HYPERTENSION AFFECTS 25% OF the adult population in North America (1), and 40% of patients with diabetes develop hypertension (32). Hypertension and diabetes account for 65-70% of all end-stage renal disease (ESRD) cases in North America (1). ESRD is a major risk factor for cardiovascular diseases, including myocardial infarction and stroke (8). While intensive insulin therapy and chronic treatment with reninangiotensin system (RAS) blockers effectively retard the progression of diabetic nephropathy, they do not provide a cure (9,14,27,28,44). Such findings, however, indicate that hyperglycemia, hypertension, and RAS activation are major risk factors in the pathogenesis of ESRD.Human and murine renal proximal tubular cells (RPTCs) express all components of the RAS (19,22,34,41). We have reported that transgenic (Tg) mice that specifically overexpress angiotensinogen (Agt), the sole precursor of angiotensins in RPTCs, develop hypertension, albuminuria, and tubular apoptosis (21, 30). Furthermore, Agt overexpression enhances tubular apoptosis in streptozotocin (STZ)-induced diabetic mice (20). Although these findings indicate that intrarenal RAS activation and hypergly...